Internal Gear Pump for a Hydraulic Vehicle Braking System

ABSTRACT

The disclosure relates to an internal gear pump for a slip-regulated hydraulic vehicle braking system, comprising one pressure piece on either side of the gear wheels of said pump. According to the disclosure, a disk consisting of wear-resistant material is arranged between the pressure piece and the gear pump. The pressure pieces can be manufactured from plastic to reduce costs.

PRIOR ART

The invention relates to an internal gear pump for a hydraulic vehicle braking system, having the features of the preamble of claim 1. An internal gear pump of this type is known from the laid-open publication DE 10 2007 054 808 A1. The internal gear pump has an internal gearwheel and an external gearwheel which is arranged in the internal gearwheel eccentrically to the latter and meshes with it. To close and seal off a pump space, the internal gear pump has, on one end face of the internal gearwheel and of the external gearwheel, a thrust piece which bears sealingly against the end faces of the gearwheels. The pump space is a space between the two gearwheels which extends in the circumferential direction from a pump inlet to a pump outlet. The thrust piece is usually in the form of a perforated disk and is pierced by a pump shaft, and it is also designated as an axial disk. A thrust piece may be arranged on both end faces of the gearwheels of an internal gear pump or only one thrust piece is present. In the latter case, the pump space is closed and sealed off on the other end face, for example, by means of a casing wall of a pump casing, the pump casing, for example, being closed on this side, or said casing wall being a casing wall located between two internal gear pumps. The casing wall may, where appropriate, be interpreted as a thrust piece.

The thrust piece of an internal gear pump must be composed of a wear-resistant material because the gearwheels otherwise become misshapen particularly in the region of their tooth tips, thus leading to leakage, impairing the efficiency of the pump and reducing a feed pressure, that is to say a pressure difference between the pump outlet and pump inlet. Since the pump inlet and pump outlet lead through the thrust piece, the latter has a complicated shape. The pump outlet and sometimes also the pump inlet often have what is known as a pressure field in the thrust piece. The pressure field is a recess which extends a little way in the circumferential direction. Producing such a thrust piece from a wear-resistant material is complicated and entails high costs because of the complicated shape.

DISCLOSURE OF THE INVENTION

The internal gear pump according to the invention having the features of claim 1 possesses a thrust piece on one end face of the gearwheels, that is to say of the internal gearwheel and of the external gearwheel of the internal gear pump. A disk with high wear resistance is arranged fixedly in terms of rotation between the thrust piece and the gearwheels and closes and seals off the pump space on this end face. The disk and/or the thrust piece may extend over the entire circumference or over part of the circumference, the disk extending at least as far in the circumferential direction as the pump space in the internal gear pump. Since the disk bears fixedly in terms of rotation against the thrust piece and no component slides along the latter, the thrust piece of the internal gear pump according to the invention is basically not subjected to wear. The invention has the advantage that the thrust piece can be composed of a cost-effective material which can easily be machined and/or is simple to produce, and it can be produced, for example, from plastic by injection molding. The disk arranged between the thrust piece and the gearwheels of the internal gear pump can be thin and therefore requires little material. The material costs of the disk can thereby be kept low, even when the disk is composed of a costly material having high wear resistance. A further advantage is that the disk can be machined more simply when it is thin.

The subclaims have as their subject matter advantageous refinements and developments of the invention specified in claim 1. Further features of the invention may be gathered from the following description of an embodiment, from the drawing and from the claims. The individual features can be implemented in each case individually or severally in any combination in embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING

The invention is explained in more detail below by means of an embodiment illustrated in the drawing in which:

FIG. 1 shows an axial section through an internal gear pump according to the invention;

FIG. 2 shows an end view of an internal gear pump from FIG. 1;

FIG. 3 shows a disk of the internal gear pump from FIGS. 1 and 2; and

FIG. 4 shows a thrust piece of the internal gear pump from FIGS. 1 and 2.

EMBODIMENT OF THE INVENTION

The internal gear pump 1 according to the invention, illustrated in FIG. 1, is a double pump with two internal gear pumps 2, 2′. Each internal gear pump 2, 2′ has an external gearwheel 3, 3′ and an internal gearwheel 4, 4′ which mesh with one another. The two gearwheels 3, 4, 3′, 4′ are arranged in one plane and eccentrically to one another. The external gearwheels 3, 3′ are fixed in terms of rotation to a pump shaft 6 with a form fit by means of star profiles 5, 5′. The two internal gear pumps 2, 2′ are accommodated in a two-part casing 7, 7′ which is divided radially and the two casing halves 7, 7′ of which are plugged together axially. A partition 8 is arranged between the two gear pumps 2, 2′.

Arranged in a pump space 10 (FIG. 2) between the external gearwheel 3, 3′ and the internal gearwheel 4, 4′ is an arcuate sickle 11 which is pivotable about a pin 12 which passes through the filler piece 11 axially parallel to the pump shaft 6. Tooth tips of the external gearwheel 3, 3′ and of the internal gearwheel 4, 4′ brush along the sickle 11. The internal gear pump 2, 2′ is therefore what is known as a sickle pump. The invention is not restricted to this form of construction of internal gear pumps, and it may also be designed, for example, as an annular gear pump (not illustrated). The pump space 10 extends, within the internal gearwheel 4, 4′, in the circumferential direction around the external gearwheel 3, 3′ from a pump inlet 13 to a pump outlet 14.

Arranged on end faces, facing away from one another, of the internal gear pumps 2, 2′ are thrust pieces 9, 9′ which have cylindrical through holes 15 for the pump shaft 6. FIG. 4 shows the end view of one of the thrust pieces 9. The thrust pieces 9 are disk-shaped, are composed of plastic and are produced by injection molding. They are in the form of segments of a circle which extend over more than 180°, that is to say occupy more than a semicircle. In addition, an oblique face 16 is cut out at the transition from a straight margin 17, running in the chord direction, to the circumference. The thrust pieces 9 have a blind hole 18 for the pin 12 of the sickle 11 and also a pressure field 19. The pressure field 19 is a clearance which is located in the end face of the thrust piece 9 and which faces the internal gear pump 2, 2′ and extends a little way in the circumferential direction and tapers in a circumferential direction. Such pressure fields are known from internal gear pumps and serve for axial hydraulic equalization at the pump inlet and/or pump outlet. In the internal gear pump 2, 2′ illustrated, the pressure field 19 communicates with the pump outlet 14, and at the pump inlet 13 the thrust piece 9 has, instead of a pressure field, the flattening caused by the margin 17 running in the chord direction.

The thrust piece 9, on the left in FIG. 1, on the closed side of the casing 7 has additionally a bearing bush 20 for the rotary mounting of the pump shaft 6. The bearing bush 20 is a one-piece component of the thrust piece 9. The thrust piece 9′, on the right in FIG. 1, has no bearing bush because the pump shaft 6 is mounted there by means of a motor bearing, not illustrated, of an electric drive motor of the internal gear pump 1, 2, 2′.

Between the thrust piece 9, 9′ and the gearwheels 3, 4, 3′, 4′ of the internal gear pumps 2, 2′ is arranged a disk 21, 21′ which is composed of metal or of another wear-resistant material. In an end view (FIG. 3), the disk 21 has the same shape as the thrust piece 9. The disk 21 closes the pump space 10 and seals off the gearwheels 3, 4, 3′, 4′ on their end faces. The disks 21, 21′ are pierced by the pump shaft 6 and the pins 12, 12′ of the sickles 11, 11′ and are thereby held fixedly in terms of rotation. Since the disks 21, 21′ are thin, they can easily be machined, even though they are composed of wear-resistant material. They have exclusively cylindrical holes which are therefore simple to produce. The disks 21, 21′ have fine control notches 22 in the end face which faces the internal gear pump 2, 2′. These are grooves which extend arcuately to a limited extent at a mean tooth depth of the gearwheels 3, 4, 3′, 4′. The fine control notches 22 ensure pressure equalization in tooth interspaces of the gearwheels 3, 4, 3′, 4′ and reduce the generation of noise by the internal gear pumps 2, 2′.

The two internal gear pumps 2, 2′ are offset at 180° to one another, that is to say their pump spaces 10 lie opposite one another, as seen in the circumferential direction.

Disks 21, 21′ are likewise arranged on those end faces of the internal gear pumps 2, 2′ which face one another, that is to say between the internal gear pumps 2, 2′ and the partition 8, such as are also arranged between the thrust pieces 9, 9′ and the internal gear pumps 2, 2′ and were explained above. The partition 8 may likewise be interpreted as a thrust piece of the internal gear pumps 2, 2′.

The pump inlets 10 and pump outlets 14 are routed through the partition 8, are located outside the sectional plane and can therefore not be seen. 

1. An internal gear pump for a hydraulic vehicle braking system, comprising: an internal gearwheel; and an external gearwheel which is arranged eccentrically in the latter and which meshes with the internal gearwheel, and a thrust piece which is arranged fixedly in terms of rotation on one end face of the external gearwheel and of the internal gearwheel, wherein a disk having high wear resistance is arranged fixedly in terms of rotation between the thrust piece, on the one hand, and the external gearwheel and the internal gearwheel, on the other hand, and seals off the gearwheels on the end face.
 2. The internal gear pump as claimed in claim 1, wherein the disk is composed of metal and/or the thrust piece is composed of plastic.
 3. The internal gear pump as claimed in claim 1, wherein the internal gear pump has a thrust piece and a disk on each end face of its gearwheels.
 4. The internal gear pump as claimed in claim 1, wherein a pump inlet or a pump outlet is cut out from the thrust piece and/or the disk.
 5. The internal gear pump as claimed in claim 1, wherein the disk has grooves on its side facing the gearwheels, in the region of teeth of the gearwheels.
 6. The internal gear pump as claimed in claim 1, wherein the thrust piece has a shaft bearing for a pump shaft of the internal gear pump.
 7. The internal gear pump as claimed in claim 1, wherein the internal gear pump is a double pump with two internal gear pumps which have a common pump shaft.
 8. The internal gear pump as claimed in claim 7, wherein the double pump has a common thrust piece between the two internal gear pumps. 